Conventionally, a heat pipe for cooling a heat generating body such as an electronic component has been known. For example, Patent Document 1 discloses a heat pipe including a pipe casing and a porous wick. Both end portions of the pipe casing in its longitudinal direction constitute a heating portion that is heated by coming into contact with a heat generating body and, for example, a cooling portion that is naturally cooled. The pipe casing is filled with a working fluid. The working fluid is constituted of a substance that undergoes phase transformation at a predetermined temperature. The working fluid is, for example, water, alcohols, or ammonia water.
The porous wick has a plurality of pores, and generates capillarity for the working fluid.
The porous wick is provided inside the pipe casing. As a result, the pipe casing and the porous wick form a cavity extending in the longitudinal direction of the pipe casing. The cavity communicates with the plurality of pores. The porous wick interconnects the heating portion and the cooling portion in the pipe casing. In general, a porous wick is constituted of a sintered body in which copper grains are sintered inside a pipe casing.
As described above, in the heat pipe of Patent Document 1, the working fluid is evaporated by heat of the heat generating body at the heating portion to become a gas. The gas passes through the cavity and moves to the cooling portion, and its heat is dissipated in the cooling portion to be liquefied. The liquefied working fluid permeates into the porous wick. Then, the working fluid is refluxed from the cooling portion toward the heating portion by the capillarity of the porous wick. Accordingly, the heat pipe of Patent Document 1 cools the heat generating body.
Patent Document 1: Japanese Patent No. 5685656